188 The Phenomena of Morphogenesis 



An important morphogenetic problem here is how far the development 

 of such a lateral structure depends on factors in the meristem from 

 which it grew and how far it is independent. Steeves and Sussex ( 1957 ) 

 removed primordia of several sizes and ages from the meristem of 

 Osmunda and other ferns and grew them in sterile culture. These de- 

 veloped normally into mature leaves just as they would have done if at- 

 tached to the plant, except for being smaller. Evidently after a certain 

 stage is reached the control of development is within the leaf itself. This 



Fig. 8-2. Early stages in development of the leaf of Linum. SI, subapical initial; x, 

 procambial elements. ( From Girolami. ) 



self-differentiation has been found in other cases and shows that the 

 organization of the plant is not as tight as it is in animals but that there 

 is some degree of independent control of differentiation in individual 

 organs. 



A branch or secondary axis differentiates by the activity of a bud aris- 

 ing in the axil of a leaf primordium (Garrison, 1955). In herbaceous 

 plants such a bud develops directly but in woody ones it has a dormant 

 period and is covered by bud scales, or cataphylls. Bud development in 

 pine has been studied by Sacher (1955) and in angiosperms by Foster 



